Method of preparing an electrochemical system operated at ambient temperatures

ABSTRACT

A non-liquid proton conductor membrane for use in an electrochemical system, under ambient conditions, the electrochemical system comprising (a) an anode plate; (b) a cathode plate; and (c) a non-liquid proton conductor membrane interposed between the anode plate and cathode plate, such that an electrical contact is formed between the anode plate and cathode plate via the non-liquid proton conductor membrane and ions flow therebetween, the non-liquid proton conductor membrane including (i) a matrix polymer dissolvable in a first solvent; (ii) an acidic multimer dissolvable in the first solvent; wherein, the matrix polymer is selected such that when the non-liquid proton conductor membrane is contacted with a second solvent, the non-liquid proton conductor membrane swells and as a result the electrical contact improves.

This is a divisional application of U.S. patent application Ser. No.08/697,835, filed Aug. 28, 1996 now U.S. Pat. No. 5,643,689.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to electrochemical systems. Moreparticularly, the present invention relates to non-liquid protonconductors such as solid polymer proton conducting membranes, for use inelectrochemical systems, under ambient conditions.

An electrochemical system includes two electrodes, referred to ascathode, where reduction occurs during use, and anode, where oxidationoccurs. When electrons flow through an electrical circuit from oneelectrode to the other, i.e., according to the above definitions fromthe anode to the cathode, charge is equalized by movement of ions fromone electrode to the other via the electrolyte.

To this end, in most electrochemical systems the electrodes areseparated therebetween by an aqueous solution, referred to as anelectrolyte, through which ions can freely move.

However, as it is not always convenient to have a liquid present in anelectrochemical system, systems were developed, wherein a non-liquidelectrolyte is employed for proton conduction. For proton conduction,non-liquid electrolytes are non-liquid proton conductors typically inthe form of an organic polymer or an inorganic material. For varioususes of non-liquid electrolytes in electrochemical systems the reader isreferred to U.S. Pat. Nos. 3,265,536 to Miller et al., 4,664,761 toZupancic et al., 5,272,017 to Swathirajan et al., 4,594,297 to Polak etal., 4,380,575 to Nakamura et al., 4,024,036 to Nakamura et al.,4,089,816 to Sano et al., 4,306,774 to Nicholson, and 4,179,491 to Howeet al.,

Since electrochemical processes are advantageously run at elevatedtemperatures, and as heat can be produced during the electrochemicalprocess, these non-liquid electrolytes have to be heat resistant.

Nevertheless, there are many electrochemical applications which are runat room temperature, i.e., ambient temperature, and due to size orcurrent use, do not produce much heat.

For use at elevated temperatures up to one hundred °C., a familiarorganic material is a Du-Pont product under the name of Nafion, whichcontains fluorinated methanesulfonic acid groups giving it its thermalstability. An example of an inorganic material frequently used in thisrange of temperatures is hydrogenuranylphosphate.

However, for ambient conditions these materials are not very convenient,as they are very expensive and do not excel in ionic conductivity atroom temperatures. Therefore, their activity is boosted by working athigher temperatures and pressures, where currents per unity of area aremaximized and as a result, less area of the expensive membrane isnecessary. For use under ambient conditions, commercially availableorganic polymer ion exchange sheets are typically employed as non-liquidelectrolytes. These however are expensive, unstable and have theadditional disadvantage of a bad electrical contact with the electrodes,which at ambient temperatures is more of a hindrance than at elevatedtemperatures.

In order to evade these problems, use of heterogeneous systems, where aninsoluble ion exchange material is mixed with a polymer, oralternatively, use of homogeneous systems, where acids like sulfuric,phosphoric or heteropolyacids are dissolved in a polymer were initiated.Nevertheless, the former still have the disadvantage of bad electricalcontact with the electrodes, while in the latter, the acidic materialtends to leach out.

There is thus a widely recognized need for, and it would be highlyadvantageous to have, a non-liquid proton conductor for use inelectrochemical systems under ambient conditions, which systems arecharacterized by (i) an electrical contact between the non-liquid protonconductor and the electrodes, which is as good as that obtained usingliquid electrolytes; and (ii) a proton conductor which by nature doesnot leach out.

SUMMARY OF THE INVENTION

According to the present invention there is provided a non-liquid protonconductor membrane for use in electrochemical systems under ambientconditions.

According to further features in preferred embodiments of the inventiondescribed below, the electrochemical system comprising (a) an anodeplate; (b) a cathode plate; and (c) a non-liquid proton conductormembrane interposed between the anode plate and cathode plate, such thatan electrical contact is formed between the anode plate and the cathodeplate via the non-liquid proton conductor membrane and ions flowtherebetween, the non-liquid proton conductor membrane including (i) amatrix polymer dissolvable in a first solvent; (ii) an acidic multimerdissolvable in the first solvent; wherein, the matrix polymer isselected such that when the non-liquid proton conductor membrane iscontacted with a second solvent, the non-liquid proton conductormembrane swells and as a result the electrical contact between the anodeplate and/or the cathode plate and the membrane, improves.

According to still further features in the described preferredembodiments the first and second solvents are water.

According to still further features in the described preferredembodiments the second solvent is externally added to the system.

According to still further features in the described preferredembodiments the electrochemical system is a fuel cell and the secondsolvent is water formed while the cell operates.

According to still further features in the described preferredembodiments the matrix polymer is selected from the group consisting ofpolyvinylidene fluoride, polyhydroxyethylene, polyethyleneimine,polyacrylic acid, polyethylene oxide, poly-2-ethyl-2-oxazoline, phenolformaldehyde resins, polyacrylamide, poly-N-substituted acrylamide,poly-4-vinylpyridine, polymethacrylic acid, poly-N-vinylimidazole,polyvinyl sulfonic acid, poly-2-vinylpyridine, polyvinylpyrrolidone,polyvinylphosphonic acid, a polymer having a hydrophilic functionalmoiety, agar, agarose, polyvinyl alcohol and mixtures thereof.

According to still further features in the described preferredembodiments the acidic multimer is obtained by acidification of anorganic multimer.

According to still further features in the described preferredembodiments the organic multimer is selected from the group consistingof polyolefins, polystyrenes, phthalocyanines, porphyrins, nylons,paraffin wax and a vinyl polymer or copolymer having a functional groupof the formula --CH₂ --!_(n).

According to still further features in the described preferredembodiments the acidic multimer is obtained by polymerization orcopolymerization of monomers.

According to still further features in the described preferredembodiments the acidic multimer is in its salt forth during thepreparation of said membrane.

According to still further features in the described preferredembodiments the acidic multimer is selected from the group consisting ofsulfonated wax, polyvinylsulfonic acid, polyvinylphosphoric acid,sulfonated polyolefins, sulfonated polystyrenes, sulfonatedphthalocyanines, sulfonated porphyrins,poly-2-acrylamido-2-methylpropanesulfonic acid, polyacrylic acid andpolymethacrylic acid.

According to still further features in the described preferredembodiments the system is a fuel cell, the anode plate and the cathodeplate contain a catalyst selected from the group consisting of platinum,palladium, rhodium, ruthenium, tin, cobalt, chromium, metalphthalocyanines, metaloporphyrins and mixtures thereof.

According to still further features in the described preferredembodiments the system is a battery, the anode plate includes a mixtureof a first ingredient selected from the group consisting of chloranilicacid and compounds (e.g., salts and oxides) containing metal ions havinga redox potential ranging between -400 to +400 mvolts versus a standardhydrogen electrode and of a second ingredient selected from the groupconsisting of acetylene black, forms of carbon like carbon black andactivated carbon, and the cathode plate includes a mixture of a thirdingredient selected from the group consisting of compounds (e.g., salts,oxides, sulfates such as manganese sulfate) containing metal ions havinga redox potential higher than one volt versus the standard hydrogenelectrode and a fourth ingredient selected from the group consisting ofacetylene black, forms of carbon like carbon black and activated carbon.

According to still further features in the described preferredembodiments the system is selected from the group consisting ofbatteries, fuel cells, capacitors and electrolizers.

According to still further features in the described preferredembodiments the non-liquid proton conductor membrane further includes afiller.

According to still further features in the described preferredembodiments the filler is selected from the group consisting of aluminapowder, titania powder, silica powder, ceria powder, polyolefin powder,polystyrene powder and their acidified derivatives.

According to still further features in the described preferredembodiments the non-liquid proton conductor membrane further includescross-links formed at least between molecules of the matrix polymer.

According to still further features in the described preferredembodiments the non-liquid proton conductor membrane further includescross-links formed at least between molecules of the acidic multimer.

According to still further features in the described preferredembodiments the non-liquid proton conductor membrane further includescross-links formed at least between molecules of the acidic multimer andmolecules of the matrix polymer.

According to still further features in the described preferredembodiments provided is a method of preparing a non-liquid protonconductor membrane for use in electrochemical systems as describedhereinabove and further described below, the method comprising the stepsof (a) dissolving a matrix polymer and an acidic multimer in a firstsolvent to obtain a homogenous solution; (b) pouring the homogenoussolution onto a surface; and (c) evaporating the first solvent to obtainthe non-liquid proton conductor membrane.

According to still further features in the described preferredembodiments provided is a method of preparing an electrochemical systemsuch as batteries, a fuel cell, a capacitor and an electrolizer,operated at ambient temperatures, the method comprising the steps of (a)dissolving a matrix polymer and an acidic multimer in a first solvent toobtain a homogenous solution; (b) pouring the homogenous solution onto asurface; (c) evaporating the first solvent and therefore obtaining anon-liquid proton conductor membrane; and (d) interposing the non-liquidproton conductor membrane in an electrical contact between an anodeplate and a cathode plate. The matrix polymer is selected such that whenthe non-liquid proton conductor membrane is contacted with a secondsolvent, the non-liquid proton conductor membrane swells and as a resultthe electrical contact improves.

According to still further features in the described preferredembodiments the methods further comprising the step of formingcross-links within the non-liquid proton conductor membrane.

According to still further features in the described preferredembodiments provided is a reference electrode for reference measurementsof non-liquid systems, the reference electrode comprising an electrodeembedded in a non-liquid proton conductor material, such that anelectrical contact is formed between the electrode and the non-liquidproton conductor material, the non-liquid proton conductor materialincluding (i) a matrix polymer dissolvable in a first solvent; and (ii)an acidic multimer dissolvable in the first solvent; wherein, the matrixpolymer is selected such that when the non-liquid proton conductormaterial is contacted with a second solvent, the non-liquid protonconductor material swells and as a result the electrical contactimproves.

The present invention successfully addresses the shortcomings of thepresently known configurations by providing a non-liquid protonconductor membrane for use in electrochemical systems under ambientconditions, the conductors according to the invention are characterizedby (i) an electrical contact which is as good as that obtained withliquid electrolytes; and by (ii) being leach proof.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention herein described, by way of example only, with referenceto the accompanying drawings, wherein:

FIG. 1 is a schematic depiction of an electrochemical system accordingto the present invention;

FIG. 2 is a schematic depiction of a reference electrode according tothe present invention; and

FIGS. 3a and 3b are plots demonstrating the dependency of the voltageand current, respectively, on time from operating a water producing fuelcell, constructed according to Example 5 of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of non-liquid proton conductor membranes i.e.,solid polymer proton conducting substrates, for use in electrochemicalsystems under ambient conditions. Specifically, the present inventioncan be used (i) to improve the electrical contact between the non-liquidproton conductor membrane and the electrodes of the electrochemicalsystem to obtain conductivity which is as good as that obtained withliquid electrolytes; and (ii) to provide an electrochemical systemhaving a proton conductor which by nature does not leach out.

The principles and operation of a non-liquid proton conductor membranesaccording to the present invention may be better understood withreference to the drawings and accompanying descriptions.

Referring now to the drawings, FIG. 1 illustrates few of the basiccomponents of an electrochemical system according to the presentinvention, generally referred to hereinbelow as system 10.

System 10 includes an anode plate 12, a cathode plate 14 and anon-liquid proton conductor membrane 16 interposed between anode plate12 and cathode plate 14, such that an electrical contact is formedbetween anode plate 12 and cathode plate 14 via non-liquid protonconductor membrane 16 and ions flow therebetween.

According to the present invention, non-liquid proton conductor membrane16 includes a matrix polymer dissolvable in a first solvent and anacidic multimer (i.e., polymer and/or oligomer) also dissolvable in thefirst solvent, such that both materials may be homogeneously dissolvedin their multimeric forms in the first solvent, which is preferablywater, and thereafter dried out to obtain non-liquid proton conductormembrane 16.

Further according to the present invention, the matrix polymer isselected such that when non-liquid proton conductor membrane 16 iscontacted with a second solvent, typically water, non-liquid protonconductor membrane 16 swells, and as a result the electrical contactbetween anode plate 12 and cathode plate 14 formed via non-liquid protonconductor membrane 16, improves.

Selecting acidic multimer which can be homogeneously mixed with thematrix polymer ensures that (i) the acidic multimer which is the protonconducting agent in the system, is uniformly distributed withinnon-liquid proton conductor membrane 16; and (ii) at the same time theacidic multimer by nature cannot leach out of the membrane, as it ishomogeneously distributed among the matrix polymer molecules.

Electrochemical systems according to the present invention may bebatteries, fuel cells, capacitors, electrolizers and referenceelectrodes used in these systems.

In batteries the electrodes (i.e., cathode and anode) contain a materialwhich is capable of redox reactions. The difference between the redoxpotential of the anode and the cathode gives the open circuit potentialof the battery. When the electrodes are connected over a load, a currentstarts to flow. In order not to lose valuable energy, it is preferredthat the voltage changes as little as possible when the current startsto flow. In this respect the resistance of the electrolyte becomesimportant. If the electrolyte is a good proton conductor, appreciablecurrents can be drawn without a drop in voltage. When the redoxreactions of the electrode are reversible, the battery is rechargeable.When, on the other hand, the redox reactions of the electrode areirreversible, the battery is a primary battery, which can be used onlyonce. Further details concerning the construction and operation ofbatteries may be found in "Handbook of Batteries", second edition,editor in chief David Linden. McGraw Hill, N.Y., 1994, which isincorporated by reference as if fully set forth herein.

The resistance of the battery depends not only on the protonconductivity of the electrolyte but also on the contact between theelectrolyte and electrodes. If the electrolyte is a liquid, there is aninherent good contact. Yet, if the electrolyte is a rigid polymer,contact may become be poor. By using a swellable matrix polymer, thephysical and thus electrical contact is tremendously improved, as thenon-liquid proton conductor membrane adapts itself to the roughness ofthe electrode surfaces as a liquid would.

Fuel cells are actually batteries where the redox materials areconstantly fed into the system, all as well known in the art. In fuelcells, an electrolyte is positioned and on both sides of which acatalyst is deposited. Hydrogen is fed towards the anode plate andoxygen towards the cathode plate. Because of the catalyst, oxygen isreduced and hydrogen is oxidized to a proton which passes through theelectrolyte where it combines with the reduced oxygen to form water.Therefore in a hydrogen/oxygen fuel cell water is produced duringoperation.

Dependent on the working temperature, many kinds of electrolytes arecurrently used in fuel cells. For ambient conditions non-liquidelectrolytes are attractive. As water is produced during the operationof the fuel cell, a non-liquid proton conductor membrane which includesa water swellable polymer will swell and make a superior contact withthe catalyst layers. The theoretical voltage of a fuel cell is 1.23volts but in practice mostly not more than 1 volt is obtained. Furtherdetails concerning the construction and operation of fuel cells may befound in "Fuel Cell Systems", edited by Leo J. M. J. Blomen and MichaelM. Mugerwa, Plenum N.Y. and London, which is incorporated by referenceas if fully set forth herein.

The opposite of a fuel cell is an electrolizer. By applying a voltageand passing water alongside the catalysts, hydrogen and oxygen areevolved. Further details concerning the construction and operation ofelectrolizers may be found in "Fuel Cell Systems", edited by Leo J. M.J. Blomen and Michael M. Mugerwa, Plenum N.Y. and London, 1993, which isincorporated by reference as if fully set forth herein.

Many reference electrodes contain a liquid and are therefore difficultto use in non-liquid systems. It is possible to use the non-liquidproton conductor material according to the invention also for making areference electrode for non-liquid systems. To this end, a referenceelectrode is made for instance from silver/silver chloride embedded inagar/agar. This system is immersed in a polymer solution containing amultimeric acid, taken out and given to dry. There is now a non-liquidproton conducting barrier between the system to be measured and thereference electrode, which prevents leaching out of the activematerials. Further details concerning the construction and operation ofreference electrodes may found in "Reference Electrodes Theory andPractice", George J. Janz and David J. Ives editors, Academic Press. NewYork and London, 1961, which is incorporated by reference as if fullyset forth herein.

With reference now to FIG. 2, according to the invention, provided is areference electrode, generally referred to hereinbelow as referenceelectrode 20 which is suitable for reference measurements of non-liquidsystems.

Reference electrode 20 includes an electrode 22 embedded in a non-liquidproton conductor material 24, such that an electrical contact is formedbetween electrode 22 and non-liquid proton conductor material 24.Non-liquid proton conductor material includes a matrix polymerdissolvable in a first solvent; and an acidic multimer also dissolvablein the first solvent. The matrix polymer is selected such that whennon-liquid proton conductor material 24 is contacted with a secondsolvent it swells and as a result the electrical contact improves.

According to preferred embodiments of the invention the second solvent(e.g., water or aqueous solution) is added to the system to swell thenon-liquid proton conductor membrane. This is the case in systems suchas batteries, capacitors, electrolizers and reference electrodes.

According to other preferred embodiments of the invention the water isformed while the electrochemical system operates. This is the case infuel cells where water is formed during the reduction of oxygen.

The matrix polymer may be of any type which will swell when contactedwith a selected solvent (e.g., water). Examples include but are notlimited to polyvinylidene fluoride, polyhydroxyethylene,polyethyleneimine, polyacrylic acid, polyethylene oxide,poly-2-ethyl-2-oxazoline, phenol formaldehyde resins, polyacrylamide,poly-N-substituted acrylamide, poly-4-vinylpyridine, polymethacrylicacid, poly-N-vinylimidazole, polyvinyl sulfonic acid,poly-2-vinylpyridine, polyvinylpyrrolidone, polyvinylphosphonic acid, apolymer having a hydrophilic functional moiety, agar, agarose, polyvinylalcohol and mixtures thereof.

The acidic multimer may be obtained by acidification of an organicmultimer, such as but not limited to polyolefins, polystyrenes,phthalocyanines, porphyrins, nylons, paraffin wax and a vinyl polymer orcopolymer having a functional group of the formula --CH₂ --!_(n).

Alternatively, the acidic multimer is obtained by polymerization orcopolymerization of suitable monomers such as but not limited to vinylsulfonic acid, vinyl phosphoric acid, acrylic acid, methacrylic acid,2-acrylamido-2-methylpropylsulfonic acid, styrenesulfonic acid and othervinylmonomers carrying an acidic group, which can be polymerized orcopolymerized in the presence or absence of other vinyl includingmonomers.

In both cases the acidic multimer may be in its salt form during thepreparation of said membrane, or its hydrogen containing form.

In preferred embodiments the acidic multimer is sulfonated wax,polyvinylsulfonic acid, polyvinylphosphoric acid, sulfonatedpolyolefins, sulfonated polystyrenes, sulfonated phthalocyanines,sulfonated porphyrins, poly-2-acrylamido-2-methylpropanesulfonic acid,polyacrylic acid or polymethacrylic acid, yet other acidic polymers arealso suitable.

When the electrochemical system is a fuel cell, the anode plate andcathode plate may contain a catalyst such as but not limited toplatinum, palladium, rhodium, ruthenium, tin, cobalt, chromium, metalphthalocyanines, metaloporphyrins and mixtures thereof.

When the electrochemical system is a battery, the anode plate includes amixture of a first ingredient such as but not limited to chloranilicacid and compounds (e.g., salts and oxides) containing metal ions havinga redox potential ranging between -400 to +400 mvolts versus a standardhydrogen electrode, and of a second ingredient such as but not limitedto acetylene black, forms of carbon like carbon black and activatedcarbon. The cathode plate includes a mixture of a third ingredient suchas but not limited to compounds (e.g., salts, oxides and sulfates suchas manganese sulfate) containing metal ions having a redox potentialhigher than one volt versus the standard hydrogen electrode, and afourth ingredient such as but not limited to acetylene black, forms ofcarbon like carbon black and activated carbon.

In some preferred embodiments the non-liquid proton conductor membranefurther includes a filler, such as but not limited to alumina powder,titania powder, silica powder, ceria powder, polyolefin powder,polystyrene powder and their acidified derivatives.

According to the invention there is also provided a method of preparinga non-liquid proton conductor membrane for use in electrochemicalsystems, which method includes the steps of (a) dissolving a matrixpolymer and an acidic multimer in a first solvent to obtain a homogenoussolution; (b) pouring the homogenous solution onto a surface; and (c)evaporating the first solvent to obtain the non-liquid proton conductormembrane.

According to the invention there is further provided a method ofpreparing an electrochemical system such as batteries, fuel cells,capacitors and electrolizers, operated at ambient temperatures, whichmethod includes the steps of (a) dissolving a matrix polymer and anacidic multimer in a first solvent to obtain a homogenous solution; (b)pouring the homogenous solution onto a surface; (c) evaporating thefirst solvent and therefore obtaining a non-liquid proton conductormembrane; and (d) interposing the non-liquid proton conductor membranein an electrical contact between an anode plate and a cathode plate. Thematrix polymer is selected such that when the non-liquid protonconductor membrane is contacted with a second solvent, the non-liquidproton conductor membrane swells and as a result the electrical contactimproves.

In a preferred embodiment, any of the methods further includes a step offorming cross-links within the non-liquid proton conductor membraneand/or including a filler within the membrane. The cross-links and/orfiller are directed at providing the membrane with physical toughness,which is important in some applications. This may permit the use ofthinner membranes which thereby improve the conductivity of theelectrolytic layer.

Reference is now made to the following examples, which together with theabove descriptions, illustrate the invention.

EXAMPLE 1 Preparation of a n on-liquid proton conductor membrane

A general scheme is herein described for the preparation of a non-liquidproton conductor membrane according to the invention.

First, a matrix polymer solution is prepared, mostly of the order of5-10% polymer, typically in water, yet other solvents, e.g., acetone,acetonitrile, alcohol, methylethylketone, dioxane, tetrahydrofuran,dimethylformamide, dimethylsulfoxide and the like are also suitabledepending on the nature of the matrix polymer and the multimeric acid,see stage 2 below.

Second, an oligomeric or polymeric (i.e., multimeric) acid, i.e., acidicmultimer, is prepared either by polymerization or copolymerization ofmonomers, or by treatment of an existing polymer or oligomer by whichacidic groups are introduced thereon. The acidic multimer thus formed,as such, or in the form of one of its salts, is dissolved in the samesolvent as used to dissolve the matrix polymer.

Third, both solutions are mixed carefully taking care that the mixturestays a clear homogenous solution.

Fourth, if the mixture contains a salt form of the multimeric acid, itcan be treated with the hydrogen form of a strongly acidic ion exchangeresin (e.g., Dowex or Amberlite beads), which may be filtered off orleft in the mixture. This results in replacement of the metal ions byprotons.

Fifth, a filler such as but not limited to alumina powder, titaniapowder, silica powder, ceria powder, polyolefin powder, polystyrenepowder and their acidified derivatives, or beads (e.g., the resin beads)can be added. The filler increases the toughness of the membrane. Ionexchange resin left in the mixture as described under the fourth stageabove may serve also the function of a filler.

And, finally, the mixture thus obtained is poured onto a surface and thesolvent given to evaporate.

For some embodiments, the physical toughness of the membrane is of greatimportance. In order to increase the toughness of the membrane, a crosslinking procedure may be employed. To this end, either a cross-linkingsubstance is added to the solution prior to the final step, wherein thesolvent is evaporated, or, a cross linking treatment such as heat and/orradiation is applied to the membrane post the final stage. In preferredembodiments, cross-links are formed at least between molecules of thematrix polymer, at least between molecules of the acidic multimer, or atleast between molecules of the acidic multimer and molecules of thematrix polymer.

EXAMPLE 2 Preparation of a fuel cell

Soft paraffin wax is dissolved in carbon tetrachloride and a quantity ofchlorosulfonic acid is added in an amount sufficient for reaching asulfonation product of 3 meq/gram. The mixture is boiled for two hours,afterwhich time an insoluble layer is formed. The solvent containingunreacted wax is decanted. After washing and drying the residue, ablackish water soluble product is obtained. This product is dissolved ina 5% polyvinyl alcohol (PVA) in water solution, such that the ratio ofsulfonated wax to PVA is 1 to 10. The obtained solution is poured on aflat surface and given to dry to obtain a non-liquid proton conductormembrane.

Fuel cell electrodes of the E-Tek Inc. (6 Mercer Road, Natick, Mass.01760 USA), containing 1 mg platinum (Pt) catalyst per one cm² arewetted with a 50% phosphoric acid solution in alcohol and the alcoholremoved by drying at 80° C. In such a way the pores characterizing thesurface of the fuel cell electrodes are partially filled with phosphoricacid. This procedure is necessary to get ionic conduction also withinthe pores where the polymer does not enter during preparation.

The non-liquid proton conductor membrane obtained above is wettedslightly with 2M phosphoric acid in order to make it sticky, and thetreated electrodes are pressed on, by which contact is made between thephosphoric acid within the pores and the membrane.

Using hydrogen as the fuel and oxygen as the oxidant, the fuel cell thusprepared has an open circuit voltage of 993 mV, and a current of 900mA/cm² can be maintained at a voltage of 102 mV. At 200 mA/cm² thevoltage is 533 mV. All data were derived under ambient conditions.

EXAMPLE 3 Preparation of a battery

A solution of 20 grams of polyvinyl alcohol (PVA) in 500 ml water isprepared. To 15 ml of the obtained solution, 0.6 grams of a 25% aqueoussolution of polyvinylsulfonic acid sodium salt is added, as well as 1gram of Dowex 50 W×8 200-400 mesh strongly acidic ion exchanger. Afterstirring, the solution is poured onto a flat surface and given to dry.

The resulting non-liquid proton conductor membrane which contains theDowex particles is interposed between two electrodes, wherein the anodeplate is a mixture of chloranilic acid and acetylene black and thecathode plate a mixture of manganese sulfate and acetylene black, bothslightly wetted with 4M sulfuric acid.

This cell cycles between 0.8 and 2.0 volts at 4 mA per cm², and iscapable of cycling for hundreds of cycles giving an energy density ofapproximately 40 mWh/cm³. All data were derived under ambientconditions.

EXAMPLE 4 Preparation of a reference electrode

A silver wire is thoroughly anodized in a chloride containing solutionin the dark. The resulting silver/silver chloride system is covered withan agar/agar layer containing chloride. After drying, it is immersed ina solution prepared as described under Example 2 above and dried. Theresulting reference electrode has a potential of 210 mV towards astandard hydrogen electrode and can be advantageously used as areference electrode in non liquid systems. All data were derived underambient conditions.

EXAMPLE 5 Preparation of a fuel cell

A solution of 20 grams of polyvinylalcohol in 500 ml of water isprepared. To 30 ml of this solution, 0.5 gram of a 25% aqueous solutionof polyvinylsulfonic acid sodium salt is carefully added. When themixture is clear, 0.5 gram of 200-400 mesh Dowex 50 W×8 acidic ionexchanger is added and mixed well, after which it is filtered off. Thesolution obtained is poured onto a flat dish and given to dry. Thenon-liquid proton conductor membrane obtained, which is transparent witha slight rose hue, is convened into a fuel cell as described underExample 2 above.

The cell thus obtained yields an open circuit voltage of 948 mV, acurrent of 750 mA/cm² can be maintained at 0.082 volts, while at acurrent of 225 mA/cm² the voltage is 501 mV. All data were derived underambient conditions.

EXAMPLE 6 Dependency of the voltage and current on time from operating awater producing fuel cell

With reference now to FIGS. 3a-b. A fuel cell was constructed asdescribed under Example 5 above and was operated against a load of fiveohms. The voltage in volts (FIG. 3a) and current in mA (FIG. 3b) wererecorded as a function of time elapsed from operating the cell. Atvarious times the swelling of the non-liquid proton conductor membranedue to water formed during the operation of the fuel cell was visuallyestimated. Most of the swelling occurred within Ca. ten minutes postoperation of the fuel cell. Swelling and therefore contact between themembrane and the electrodes has intensified after Ca. six minutes to adegree that it was practically impossible to separate them withoutcausing irreversible damage to the cell.

Note that the increase in voltage and currents until reaching a plateauparallels the swelling of the membrane, indicative of the formation ofan improved electrical contact between the membrane and the electrodesof the fuel cell as the membrane swells.

EXAMPLE 7 Preparation of a fuel cell

The same procedure as described under Example 5 above was followed. PVAsolution, polyvinylsulfonic acid sodium salt aqueous solution and Dowexpowder are mixed and the Dowex filtered off. To the clear solutionobtained, 50 mg of alumina powder filler are added and the mixturepoured onto a flat surface and given to dry, resulting in a toughenedmembrane. A fuel cell as described under Example 2 above was preparedusing this non-liquid proton conductor membrane. The cell yields an opencircuit of 721 mV, a current of 800 mA/cm² can be maintained at 80 mV,while at a current of 225 mA/cm², the voltage is 484 mV. All data werederived under ambient conditions.

EXAMPLE 8 Preparation of a fuel cell

A fuel cell is prepared as described under example 2 above.

Using hydrogen prepared in situ as the fuel, and air as the oxidant (noauxiliary means employed), the fuel cell thus prepared has an opencircuit voltage of 600 mV, and a current of 200 mA/cm² can be maintainedat a voltage of 327 mV. All data were derived under ambient conditions.

Preparing hydrogen in situ may for example be by reacting a hydridecompound (e.g., a metal hydride such as sodium hydride, a metalborohydride such as sodium borohydride, or a compound containing a metalhydride such as lithium aluminum hydride) or an elemental metal (e.g.,sodium) with a compound that contains protons such as but not limited towater, acidic compounds, etc., in which reaction molecular hydrogen isreleased at ambient conditions.

While the invention has been described with respect to a limited numberof embodiments, it will be appreciated that many variations,modifications and other applications of the invention may be made.

What is claimed is:
 1. A method of preparing an electrochemical systemselected from the group consisting of batteries, fuel cells, capacitorsand electrolizers, operated at ambient temperatures, the methodcomprising the steps of:(a) dissolving a matrix polymer and an acidicmultimer in a first solvent to obtain a homogenous solution; (b) pouringsaid homogenous solution onto a surface; and (c) evaporating said firstsolvent and therefore obtaining a non-liquid proton conductor membrane;and (d) interposing said non-liquid proton conductor membrane in anelectrical contact between an anode plate and a cathode plate;wherein,said matrix polymer is selected such that when said non-liquid protonconductor membrane is contacted with a second solvent, said non-liquidproton conductor membrane swells and as a result said electrical contactimproves.
 2. A method as in claim 1, further comprising the step offorming cross-links within said non-liquid proton conductor membrane.